Methods and hydraulically expandable self-cleaning sand screens

ABSTRACT

A method for cleaning a helical spring screen deep in a well while filtering liquid comprises (1) injecting a high pressure hydraulic surge pulse into the spring screen for expanding the coils, (2) forcing high pressure liquid between the coils of the helical spring screen simultaneously with expanding of the coils for washing the sand from between the coils, and (3) forcing the coils together following their expansion by expanding action of a second spring for crushing and dislodging any sand therebetween the coils for removal upon subsequent spreading of the coils. A second method is disclosed likewise. Methods for forming a self-cleaning helical spring screen and two modifications of a helical spring screen are disclosed herein for being cleaned for a multiplicity of times without having to shut the well in for workover, thus saving workover costs and lost production.

BACKGROUND OF THE INVENTION

Certain hydrocarbon-bearing formations, especially those found atshallow depth, consist of semi- and unconsolidated sands that presentproblems during production. One such problem is movement of sandparticles with produced fluids. This results in clogged bottomholescreens and reduced production, necessitating periodic cleaning of thewell and screen or replacement of the latter. Present practice requiresthe use of work-over rig equipment, opening the well, insertion of toolsoperated from the surface and mechanically carrying out the cleaningoperation.

OBJECTS OF THE INVENTION

Accordingly, a principal object of this invention is to provide at leasttwo methods for cleaning a helical spring screen by spreading the coilsapart and simultaneously washing the foreign material from between thecoils with high pressure liquid in the screen.

Another principal object of this invention is to provide at least twomethods for forming or assembling a helical spring screen.

A still further principal object of this invention is to provide atleast two hydraulically operated expandable self-cleaning sand screensthat may be cleaned for a multiplicity of times before being brought tothe surface.

A further object of this invention is to provide at least two methodsfor cleaning a helical spring screen, at least two methods forassembling a helical spring screen, and a few hydraulically operatedself-cleaning helical spring screens that are easy to operate, are ofsimple configuration, are economical to build and assemble, and are ofgreater efficiency for the filtering or screening of sand from producedoil.

Other objects and various advantages of the disclosed self-cleaninghelical spring screens and methods will be apparent from the followingdetailed description, together with the accompanying drawings, submittedfor purposes of illustration only and not intended to define the scopeof the invention, reference being made for that purpose to the subjoinedclaims.

BRIEF DESCRIPTION OF THE DRAWING

The drawing diagrammatically illustrates by way of example, not by wayof limitation, one form of the invention wherein like reference numeralsdesignate corresponding parts in the several views in which:

FIG. 1 is a schematic diagrammatic vertical sectional view with parts insection of the new sand screen as mounted in a typical oil well;

FIG. 2 is a schematic longitudinal sectional view of one modification ofthe new sand screen;

FIG. 3 is an enlarged schematic longitudinal sectional view of a secondmodification of the new sand screen, and

FIG. 4 is a section at 4--4 on FIG. 3.

The invention disclosed herein, the scope of which being defined in theappended claims is not limited in its application to the details ofconstruction and arrangement of parts shown and described, since theinvention is capable of other embodiments and of being practiced orcarried out in various other ways. Also, it is to be understood that thephraseology or terminology employed here is for the purpose ofdescription and not of limitation. Further, many modifications andvariations of the invention as hereinbefore set forth will occur tothose skilled in the art. Therefore, all such modifications andvariations which are within the spirit and scope of the invention hereinare included and only such limitations should be imposed as areindicated in the appended claims.

DESCRIPTION OF THE INVENTIONS

This patent includes three inventions, two methods for cleaning ahelical spring sand screen, two mechanisms for practicing the abovemethods comprising two modifications of a hydraulically operatedself-cleaning helical spring sand screen, and two methods for assemblinga self-cleaning helical spring sand screen.

METHODS FOR CLEANING A HELICAL SPRING SCREEN

Primarily, the method disclosed herein for cleaning a sand filter orscreen (16 or 16a) comprising a flexible screen formed of rectangularspring wire coiled into a helical spring screen (19) inside an openhousing (24) positioned deep in a petroliferous unconsolidated sandstratum or an oil well, for example, having a production tube (22)extending into the screen comprises the steps of,

(1) injecting a high pressure hydraulic surge pulse from the productiontube (22) into the helical spring screen (19) for expanding the coils ofthe helical spring screen, and

(2) forcing high pressure oil between the coils of the helical springscreen simultaneously with expanding of the coils for washing the sandfrom between the coils.

Another method for cleaning a helical spring screen having a productiontube extending into the screen for producing sand-free liquid comprisesthe steps of,

(1) expanding the coils of the helical spring screen (19) by generatinga high pressure hydraulic pulse in the helical spring screen, and

(2) washing the coils of the helical spring screen simultaneously withstep (1) above by forcing high pressure liquid between the coils fromthe high pressure hydraulic surge pulse for washing out the sand frombetween the coils.

A third method step which may be added to either of the above methodsfor additional cleaning comprises,

(3) forcing the coils together following their expansion and attenuationof the hydraulic pulse by expanding action of a second spring (26 or26a) that was compressed by the first method step, for crushing the sandtherebetween the coils for removal upon subsequent spreading of thecoils.

Two more specific and different methods are formed by adding twodifferent third steps to the above generic method:

(3) Moving a piston (25, FIG. 2) slideable on the production tube (22)and connected only to one end of the helical spring screen (19) with thehigh pressure hydraulic pulse to expand the coils of the helical springscreen for washing the sand from between the coils thereof with the highpressure liquid.

The third step for the other method for a particularly long filtercomprises:

(3) Contracting a plurality of spaced apart coils of the helical springscreen with lifter bar tabs (29a-29d, FIG. 3) for spreading apart allcoils by substantially the same distance for each being cleaned equallyby the high pressure liquid.

METHOD FOR ASSEMBLING A HELICAL SPRING SCREEN

The above described helical spring screen may be assembled by variousmethods. However, the preferred method for assembling the screenassembly (16 or 16a) for use on a production tube (22) for producingsand-free liquid comprises the following steps,

(1) forming an open housing (24) with a piston (25) and cylinder (23) onone end and a base (20) on the other end spaced a predetermined distancefrom the piston when in a neutral position, and

(2) securing the opposite ends of a helical spring screen (19) of apredetermined length to the piston and the housing base whereby upongeneration of a hydraulic pulse in the helical spring screen, the coilsof the helical spring screen are expanded and separated for cleaningthereof.

A more detailed method for forming or assembling a helical spring screenmay comprise the following steps,

(1) forming a closed ended cylinder (23) with an opening in the closedend for the production tube (22) to extend through,

(2) slideably mounting a piston (25) in the cylinder,

(3) forming an opening in the piston for its sliding movement around theproduction tube,

(4) fixedly securing a base (20) of a housing (24) at a predeterminedfixed distance from a neutral position of the piston, and

(5) fixedly securing the opposite ends of a helical spring screen of apredetermined length to the base and piston respectivley, whereby upongeneration of a hydraulic surge pulse from the production tube into thehelical spring screen, the helical spring screen is expanded and thecoils thereof washed clean.

In greater detail, the second method step may comprise further,

(1) mounting a short spring (26) between the piston and the cylinderclosed end whereby upon expansion of the helical spring screen, thepiston is moved due to the surge pulse to compress the short spring sothat upon attenuation of the surge pulse, the expanding short springcollapses the helical spring screen to crush the sand between the coilsthereof for removal upon subsequent spreading of the coils.

For more details, the fourth method step may include further,

(1) Fixedly securing a plurality of rigid bars (24) around the helicalspring screen (19) between the cylinder and the base of the assembly formaintaining the assembly base at a predetermined fixed distance from thepiston.

More details for forming one modification (FIG. 2) in the last methodstep comprise,

(1) fixedly securing one end of the helical spring screen (19) to thecylinder base (20), and

(2) fixedly securing the other end of the helical spring screen (19) tothe piston (25) for pulling on and expanding the helical spring screenupon occurrence of a surge pulse, this connection being the soleconnection for pulling and expanding the helical spring screen.

Details of a method for forming a second particularly long modification(FIG. 3) of the assembly are set forth by adding the last steps,

(1) fixedly attaching one end of a lifter bar (28a) to the piston (25a),

(2) fixedly attaching equally spaced apart tabs (29a-29d) on the lifterbar, and

(3) fixedly attaching equally spaced apart lugs (30a-30d) on the helicalspring screen coils (19a) for being contacted by the corresponding tabsfor evenly expanding the helical spring screen along its full lengthfrom the assembly base upon occurrence of the surge pulse for equaldistribution of spacing between the coils of a particularly elongatedhelical spring screen.

THE PREFERRED EMBODIMENTS FOR PRACTICING THE INVENTION

The above methods for cleaning a helical spring sand filter may beperformed by other mechanisms than that disclosed in the FIGURES. Themechanism disclosed herein may be operated by or made by other methodsthan those disclosed, as by hand. However, the preferred assemblies forperforming the method are disclosed in FIGS. 2, 3, and 4.

ARTICLES FOR PERFORMING THE METHODS

FIG. 1 is a schematic diagrammatic view of a typical producing oil well10 having pumping equipment 11 comprising motor means 12 for actuatingwalking beam 13 with horse head 14 for operating pump 15 in the well. Acrude oil pump is utilized after free flow has ceased for raising theoil that has passed through the filter 16 from the petroliferousunconsolidated sand 17 up to the surface to exit from discharge pipe 18.Except for the filter 16, all of the above parts may be conventionalelements.

FIG. 2 illustrates a schematic enlarged sectional view of the preferredmodification of the new self-cleaning helical spring filter 16a forperforming the above-described methods.

EMBODIMENT OF FIG. 2

FIGS. 2 and 3 illustrate schematic sectional views of two preferredmodifications of the new self-cleaning helical spring filter of screenassemblies 16 and 16a, respectively.

While various shapes may be utilized for the wire or bar stock forforming the helical spring 19, per se, rectangular cross-sectioned barstock of a suitable alloy is preferred in this case.

FIG. 2 illustrates helical spring screen assembly 16 having a base 20connected to a packer 21, FIG. 1, fixed in the well at the level of theunconsolidated petroliferous sand strata 17. A production tube 22protrudes down through a closed ended cylinder 23, FIG. 2, into thehelical spring screen 16 and carries the sand-free liquid, as crude oilfor example, to the surface after having passed through and having beenfiltered by the helical spring screen 19. The closed ended cylinder 23is held rigidly spaced from the assembly base 21 with a plurality ofrigid bars 24. While the rigid support means between the cylinder andbase may be any suitable perforated wall or the like, the three bars28a, 28b and 28c, FIG. 4 are preferred for forming the open housing.

Helical spring screen 19 is positioned between and fixedly secured tobase 20 and an annular piston 25 slideably mounted on the productiontube 22 and in the cylinder 23.

A short compression spring 26, FIG. 2, is squeezed or positioned betweenthe closed end or top of the cylinder 23 and the piston 25 so that withthe spring in balance or neutral position, it maintains the helicalspring screen 19 compressed by the exact amount to space its coils apartby the precise predetermined distance to filter the sand from the oil asthe sand-bearing oil flows from the unconsolidated petroliferous sandstrata 17 into the helical spring screen, where the filtered oil then ispumped up through the production tube 22 to the surface.

Discharge pipe 18, FIG. 1, also includes a conventional hydraulic surgeor pulse generator 27 for generating a hydraulic surge or pulse backdown the production tube 22 and into the helical spring screen 19.

In operation of the helical spring filter or screen assembly 16, FIG. 2,when a gradual build up of resistance to oil flow through the screen isdetected, that indicates that the helical spring screen 19 is becomingclogged with sand. One or more hydraulic pulses are then generated inthe production tube by pulse generator 27 which thus reaches the helicalscreen 19 to suddenly and instantly force the piston 25 up to compressthe small spring 26 and stretch the helical screen 19 to separate itscoils. Simultaneously, outward rushing liquid flow occurs, forcing allloose sand grains into the region surrounding the well. Subsequentattenuation of the hydraulic pressure pulse and drop of the piston 25 byexpanding action of the small compression spring 26 forces the adjacentscreen coils together hard in contact with each other for furtherloosening of adhered sand grains. The above cycle may be repeatedsufficiently until the screen is cleaned out as indicated by reducedresistance to flow detected at the surface. This would be indicated by areduction in the peak pressure associated with the hydraulic pulses.

Various piston pumps or hydraulic pulse generators, such as but notlimited to, an electromagnetically powered plunger 27 may be utilizedfor generating the hydraulic pulse down the closed-system well casing orproduction tube 22 and into the screen assembly 16. Frequency of thepulses is chosen to optimize hydraulic power transmission according tothe properties of the screen and wellbore depth.

MODIFICATION OF FIGS. 3 & 4

A modified helical spring screen assembly 16a is disclosed in FIG. 3,when a particularly long helical spring 19a is utilitized. When usinglong helical springs, if only the upper end were stretched upwardly, theupper coils would flex the greatest amount producing an unequal spacingbetween all of the coils for the complete length of the helical spring.

Accordingly, the extra long helical spring screen assembly 16a of FIG. 3has further novel features for ensuring equal spacing of all coils ofthe elongated helical spring screen 19a as it is flexed, i.e., as it isexpanded and contracted from a neutral position of screening orfiltering liquid from the adjacent formation.

Similar to the first modification 16 of FIG. 2, the helical springscreen 19a of FIG. 3 is fixedly secured at its ends to base plate 20aand piston 25a for compressing and storing energy in small spring 26a.Additional novel features comprise three lifter rods 28a, 28b, and 28crigidely connected, as by welding, to piston 25a and extending downinternally of the helical spring screen to near the bottom, but notwithin reach of it with maximum contraction of the helical spring. Fourtabs 29a, 29b, 29c, and 29d, FIG. 3, for example, are equally spacedalong and secured to each of the lifter rods, only those on rod 28abeing illustrated. Also, a set of four lugs 30a, 30b, 30c, and 30d, FIG.3, is fixedly secured, as by welding, to four corresponding coilsopposite each set of tabs. While this number of four is merely examplaryfor the illustrated helical spring screen, any suitable number may beused, depending on the length of the spring and size of the coils. Lugs(not shown) are likewise provided for the corresponding tabs on theother lifter rods (not shown).

The gaps "e" between each tab 29 and its respective lug 30 is calculatedor shown below for ensuring substantially equal spacing between thecoils for the full length of the spring for the full lift stroke of thepiston 25a at the top.

e₁ =1/5Δ

e₂ =2/5Δ

e₃ =3/5Δ

e₄ =4/5Δ

e_(i) =i/n

Where:

Δ=total upward movement of piston or top coils of spring.

e₁ =gap or clearance between tab 29a and lug 30a comprising the firstpair.

e₂, e₃ or e₄ =gaps for the remaining pairs.

e_(i) =gap or clearance between a particular pair of tabs and lugs.

n=number of equal intervals between tabs.

i=number of pairs of tabs and lugs or n-1, beginning at the top.

FIG. 4, a section at 4--4 on FIG. 3, illustrates the helical springscreen 19a inside the open housing 24a.

In operation of the modified helical spring filter or screen assembly16a, FIGS. 3 and 4, upon the filter becoming clogged, a hydraulic pulseis generated by pulse generator 27, FIG. 1, for passing down theproduction tube into the middle of the helical spring screen assembly.Instantly with occurrence of the high pressure hydraulic pulse, thepiston 25a is forced upwardly rapidly to raise the lifter rods 28a-28d,FIG. 4, upwardly by at least a distance Δ in the example above. Thedistance Δ is exaggerated in FIG. 3, as distance e₄ represents 4/5 Δ.With such a long helical spring, only the upper one fifth portion of thespring, for example, would be stretched and only the coils therein thatportion would separate the most with uneven and unequal separation overthe entire length of the helical spring screen.

Accordingly, in the modification of FIG. 3, after the piston has movedupwardly through one fifth the distance or a distance of e₁ of the totaldistance Δ in the above example, and the piston has lifted the firstcoil by a distance of e₁, then the lifter bar tab 29a contacts lug 30afor lifting the top coil of the second one fifth section of the helicalspring. While not illustrated, lifter bars 28b and 28c likewise havetabs thereon for contacting their corresponding spring lugs similar totabs 29a-29d and lugs 30a-30d. Upon the piston and lifter bar havingtraveled upwardly by a distance of two fifths the total distance Δ or adistance of the gap e₂, tab 29b contacts lug 30b for raising the topcoils of the third fifth of the total distance Δ to be traveled. Thentab 29c contacts lug 30c to separate the coils of the fourth fifth ofthe helical spring screen. Finally upon the piston and lifter barsbeginning the final one fifth of the lift, tab 29d contacts lug 30d toseparate the coils of the lowest and last section of the helical springscreen. Accordingly, upon reaching at least a distance Δ of upwardtravel of the piston and lifter bars where the spring 26a has becomecompressed and the upward force of the hydraulic pulse has attenuated,all coils of the long helical spring screen or filter have separated bysubstantially an equal amount, the maximum amount of liquid is passingbetween the coils for cleaning thereof.

The liquid continues to exit rapidly between the coils as the smallspring forces the piston 25a and helical spring screen 19a downwardly tocontract to closed or collapsed position. As all coils thus suddenlycontact each other with almost an equal force as that expanding them,most remaining foreign material, as sand, is dislodged from the surfacesof the coils and removed upon subsequent expanding and flow of liquidbetween the coils. The above cycle may be repeated, if so desired, untilthe screen is cleaned and the resistance to flow therethrough isreduced. This would be indicated by a reduction in the peak pressureassociated with the hydraulic pulses. Again, frequency of the pulses ischosen to optimize hydraulic power transmission according to theproperties of the screen and wellbore depth.

Obviously other methods may be utilized for cleaning or for forming orassembling the embodiments of either FIG. 2 or FIG. 3 than those listedabove, depending on the particular amount of complexity that can betolerated in a filter.

Accordingly, it will be seen that while only two modifications have beendisclosed, both will operate in a manner which meets each of the objectsset forth hereinbefore.

While only two methods for filtering and two methods for forming afilter of the invention have been disclosed, it will be evident thatvarious other methods and modifications are possible in the arrangementand construction of the disclosed two helical spring screen assemblieswithout departing from the scope of the invention and it is accordinglydesired to comprehend within the purview of this invention suchmodifications as may be considered to fall within the scope of theappended claims.

We claim:
 1. A method for assembling a helical spring screen assemblyfor use on a production tube for producing sand-free liquid, theproduction tube having means for generating a pulse therein comprisingthe steps of,(a) forming a closed ended cylinder with an opening in theclosed end for the production tube to extend through, (b) slideablymounting an annular piston in the cylinder for sliding movement aroundthe production tube from a neutral position, (c) securing a housing tothe cylinder with a base at a predetermined fixed distance from thepiston neutral position, and (d) fixedly securing the opposite ends of ahelical spring screen between the base and the annular piston,respectively, whereby upon generation of a hydraulic pulse in thehelical spring screen, the helical spring screen is expanded and thecoils thereof washed clean.
 2. A method as recited in claim 1 whereinthe second step (b) may include further,(a) mounting a short springbetween the piston and the cylinder closed end whereby upon expansion ofthe helical spring screen, the annular piston is moved due to the pulseto compress the short spring so that upon attenuation of the pulse, theexpanding short spring collapses the helical spring screem to furtherloosen adhered sand grains between the coils thereof for removal uponsubsequent spreading of the coils.
 3. A method as recited in claim 1wherein the third step (c) may include further,(a) fixedly securing aplurality of rigid bars for forming the housing around the helicalspring screen between the cylinder and the base of the assembly formaintaining the assembly base at the predetermined fixed distance fromthe piston neutral position.
 4. A method as recited in claim 1 whereinthe last step (d) includes further,(a) fixedly securing one end of thehelical spring screen to the housing base, and (b) fixedly securing theother end of the helical spring screen to the annular piston as the soleconnections on the helical spring screen for pulling on and expandingthe helical spring screen upon occurrence of a hydraulic pulse.
 5. Amethod as recited in claim 1 wherein the last step (d) includesfurther,(a) fixedly attaching one end of a lifter bar to the annularpiston, (b) fixedly attaching spaced apart tabs on the lifter bar, and(c) fixedly attaching spaced apart lugs on the helical spring screencoils for being contacted by the corresponding tabs for evenly expandingthe helical spring screen along its full length from the base uponarrival of the hydraulic pulse for equal distribution of spacing betweenthe coils of a particularly elongated helical spring screen.
 6. A methodfor assembling a helical spring screen assembly for producing sand-freeliquid when lowered in a well comprising the steps of,(a) forming anopen housing with a piston and cylinder on one end and a base on theother end spaced a predetermined distance from the piston when in aneutral position, and (b) securing the opposite ends of a helical springscreen of a predetermined length to the piston and the housing basewhereby upon generation of a hydraulic pulse in the helical springscreen, the coils of the helical spring screen are expanded andseparated for cleaning thereof.
 7. A self-cleaning sand screen assemblyfor producing sand-free liquid from a production tube extending downinto the assembly when lowered into a well comprising,(a) helical springscreen means mounted in a housing between a base in one end of thehousing and piston means in a cylinder in the other end of the housing,the production tube protruding down into the cylinder, (b) second springmeans for maintaining the piston means at a neutral position where apredetermined spacing is provided between said helical spring screenmeans coils for filtering the inflowing liquid, (c) means for generationa high pressure hydraulic pulse in the liquid in the helical springscreen means, and (d) said piston means being responsive to said pulsegenerator means for expanding said helical spring screen means and forsimultaneously forcing high pressure liquid between the coils of saidexpanding helical spring screen means for cleaning thereof.
 8. Aself-cleaning helical spring screen assembly for producing sand-freeliquid from a production tube extending down into the top of theassembly when lowered in a well comprising,(a) an open housing meanscomprising a closed ended cylinder having a piston means therein formingone end of the housing means with a production tube extending thereinand a base forming the other end of the housing means spaced at apredetermined distance from a neutral position of the piston, (b)helical spring screen means mounted in the housing means between saidpiston means and the housing base for being expanded by a hydraulicpulse in the helical spring screen means for separating the spring coilsfor cleaning thereof by expulsion of the liquid between the expandedcoils.
 9. A self-cleaning sand screen assembly as recited in claim 8wherein,(a) a second spring means being positioned between the closedend of said closed ended cylinder and said piston in its neutralposition for spacing all coils of said helical spring screen at apredetermined distance for filtering sand from the liquid in the wellfor producing sand-free liquid through the production tube.
 10. Aself-cleaning sand screen assembly as recited in claim 9 wherein afterthe hydraulic pulse has attenuated and said second spring means beginsto expand,(a) said piston means being responsive to said expandingsecond spring means rebound stroke for compressing said helical springscreen means for forcing all coils together for forcing loose any sandgrains therebetween for removal upon subsequent spreading of the coils.11. A self-cleaning sand screen assembly as recited in claim 8wherein,(a) said housing means comprises rigid bars connected betweensaid base and said closed ended cylinder around the production tube forforming said open housing means for housing said helical spring screenmeans.
 12. A self-cleaning sand screen assembly as recited in claim 8comprising further,(a) hydraulic pulse generating means for saidproduction tube for generating said hydraulic pulse, and (b) said pistonmeans is formed annular shaped for being slideable in said cylinderaround said production tube lower end for both expanding said helicalspring screen means responsive to said hydraulic pulse generating meansand for contracting said helical spring screen means responsive toattenuation of said hydraulic pulse for thorough cleaning of the coils.13. A self-cleaning sand screen assembly as recited in claim 8comprising further,(a) connecting means between said piston andone endof said helical spring screen means, and (b) said connecting means beingthe sole connection between said piston and the helical spring screenfor expanding the helical spring screen coils for being cleaned.
 14. Aself-cleaning sand screen assembly as recited in claim 8 comprisingfurther,(a) lifter bar means connected to said piston, (b) equallyspaced apart tabs for said lifter bar means, (c) precisely spaced apartlugs for said helical spring screen means upon occurrence of a hydraulicpulse for ensuring equal spacing between said coils of said helicalspring screen means upon full expansion for equal cleaning action on allcoils.